POS0316 SEMIQUANTITATIVE ASSESSMENT OF SYNOVITIS ON US-GUIDED SYNOVIAL MEMBRANE BIOPSIES IS CONTINGENT ON DISEASE PHASE AND PREDICTIVE OF TREATMENT RESPONSE IN NAIVE TO TREATMENT PSORIATIC ARTHRITIS
Authors: D. Bruno, B. Tolusso, M. Gessi, C. DI Mario, M. R. Gigante, L. Petricca, S. Perniola, A. Paglionico, V. Varriano, G. Peluso, L. Bui, A. Elmesmari, D. Somma, M. A. D’agostino, M. Kurowska-Stolarska, E. Gremese, S. Alivernini
Journal: Annals of the Rheumatic Diseases (2022)

Background Ultrasound (US)-guided minimally invasive Synovial Tissue (ST) biopsy serves as a safe and well tolerated procedure for basic and translational research on chronic inflammatory joint disease. Objectives (i) to assess the diagnostic value of the Krenn score (KSS) on ST samples obtained from US-guided biopsies in a large bio-samples dataset of patients with Psoriatic Arthritis (PsA) across different disease phases; (ii) to develop a multiparametric nomogram integrating clinical and histological characteristics enabling treatment response prediction in naïve to treatment PsA. Methods 410 patients fulfilling the CASPAR criteria for PsA who underwent US-guided ST biopsy were enrolled. At baseline, patients were categorized based on their disease phase and treatment: n=207 naïve to DMARDs; n=101 resistant to c-DMARDs; n=48 resistant to b-DMARDs and n=54 in sustained clinical and ultrasound remission or in low disease activity (LDA) state (DAPSA ≤ 4 or among 4-14, respectively). Clinical, demographic, and immunological characteristics were recorded for each patient. All ST specimens were stained with H&amp;E and classified by a pathologist, blinded to clinical characteristics, using the Krenn score to assess ST inflammation degree (1) implemented with the determination of lymphocytes, plasma cells, granulocytes and tissue oedema presence. Each naive to treatment PsA was treated according to the EULAR recommendations (2) and DAPSA remission rate at 6 months was recorded. Results Considering the whole enrolled cohort, the distribution of KSS was significantly different among patients across the different PsA phases (ANOVA p&lt;0.001). In particular, among the different phases, KSS was significantly higher in b-DMARDs resistant (p&lt;0.0001) and c-DMARDs resistant (p&lt;0.0001) compared to remission/LDA disease patients as well as naive to treatment PsA (p&lt;0.0001). Interestingly, regardless to the disease phase, KSS of the biopsied joint directly correlated to disease activity in terms of DAPSA (r=0.476, p&lt;0.001) and DAS28 scores (r=0.476, p&lt;0.001). Considering the naïve to treatment PsA cohort, patients achieving DAPSA defined-LDA/remission had, before treatment, significantly lower KSS (p&lt;0.001), lower rate of ST plasmacells presence (p&lt;0.001) and shorter symptoms duration (p=0.01) as compared to naïve to treatment PsA not achieving this clinical outcome. Moreover, considering distinct clinical phenotype domains, naive to treatment PsA patients with concomitant dactylitis and skin disease were less likely to achieve DAPSA LDA/remission (p&lt;0.001), regardless of treatment scheme. On logistic regression, at baseline, having a KSS &lt;5 [OR: 5.30 (95%CI:2.21-12.74) p&lt;0.001], absence of plasma cells ST infiltrate [OR: 3.87 (2.11-7.10 95%CI) p&lt;0.001], concomitant dactylitis [OR: 2.55 (95%CI:1.24-5.25) p=0.01] and skin involvement [OR: 2.06 (95%CI:1.17-3.62) p=0.01] were independent factors associated with DAPSA score-LDA/remission achievement at 6 months. Finally, a multiparametric nomogram integrating baseline clinical and histological characteristics of naïve PsA enabling to predict up to 75% of probability to achieve DAPSA remission at 6 months was developed. Conclusion KSS is a reliable tool for synovitis assessment in PsA, being contingent on disease phases, related to disease burden and included within a treatment response predictive multiparametric nomogram in naïve PsA. References [1]Krenn V, et al. Histopathology 2006 [2]Gossec L, et al. Annals of the Rheumatic Diseases 2020 Disclosure of Interests None declared